The present invention relates to a clamping system for clamping a workpiece or workpiece fixture to the supporting table of a machine tool, and in particular to a bayonet clamping system which is suitable for use with work tables when the fixture is floatingly supported on a film of pressurized air during movement from one machining position to another.
Whenever a workpiece is machined, it must be accurately positioned on the work table in proper spatial relationship to the cutting tool. Since the tool will exert considerable force on the workpiece during machining, it is also necessary that it be securely anchored or clamped in the desired position. Heretofore, work tables have been provided with T-slots normally running the entire length of the table and adapted to receive T-bolts or other fastening elements which engage clamping bars or the like for the purpose of clamping the workpiece to the table. A serious drawback to this arrangement is that considerable amounts of chips, shavings, and other debris produced during machining collect in the T-slots and frequent table clean-up by the operator is necessary.
An even more serious problem exists in work tables of the type wherein the fixture is supported for movement on a film of pressurized air. A work table of this type is shown and described in the above-identified patent and is designed to eliminate the time consuming, laborious positioning of the workpiece or fixture in the machine tool as various regions of the workpiece are to be machined. In this apparatus, the table has passages therein which supply fluid under pressure between the downwardly facing surface of the fixture and the upwardly facing horizontal surface of the table so that the fixture "floats" on the film of air and can be moved about easily on the table. Cooperating elements of pin and socket locating devices on the fixture and table provide for the accurate locating of the fixture in predetermined positions on the table.
It is necessary, however, to clamp the fixture to the table so that it will not move during positioning. Heretofore, T-slots have been used for clamping the fixture but, due to the fact that they extend underneath the fixture itself, leakage of pneumatic pressure from the film of air has resulted. This increases the pneumatic pressure which is necessary to support the workpiece. Furthermore, much of the benefits of being able to rapidly reposition the workpiece are never realized due to the cumbersome clamping operation which is necessary prior to machining.